Seasonal changes in exoplanet’s atmosphere could signal alien life

This contrasting artistic image of an early Martian environment with a thicker atmosphere (left) and the cold, dry Mars of today (right) shows how atmospheric changes affect a planet’s ability to hold life.

Researchers aim to expand our ability to hunt for aliens by creating a new search protocol to be used with next-generation telescopes. As described in a paper published yesterday (May 9) in The Astrophysical Journal Letters, a research team at University of California, Riverside’s (UCR) Alternative Earths Astrobiology Center has used the way Earth’s atmosphere changes from season to season to develop a model for chemical signs that could indicate life.

Unfortunately, single atmospheric gas measurements have the potential to be misleading. Typical biosignatures like the presence of oxygen and methane can be produced without the presence of any life, so false positives and confusing data are an issue, Edward Schwieterman, a NASA Postdoctoral Program fellow at UCR and co-author on the new work, said in a statement.

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By observing seasonal changes in these biosignatures, instead of the biosignatures alone, you have more information about the potential for life, according to lead author Stephanie Olson, a graduate student in UCR’s Department of Earth Sciences.

Olson and her team developed this unique framework, which shows how seasons and sunlight can affect atmospheric composition. Such seasonal changes to Earth’s atmosphere are affected by life; for instance, more plants grow in summer, leading to less carbon dioxide and more oxygen over the region where it’s occurring, according to the statement.

“Atmospheric seasonality is a promising biosignature because it is biologically modulated on Earth and is likely to occur on other inhabited worlds,” Olson said in the statement. “Inferring life based on seasonality wouldn’t require a detailed understanding of alien biochemistry because it arises as a biological response to seasonal changes in the environment, rather than as a consequence of a specific biological activity that might be unique to the Earth.”

While this work is specific to Earth, scientists could use this framework to study alien planets as well, Olson explained. Although the telescope technology that would ideally use this framework is still on its way, “It’s really important that we accurately model these kinds of scenarios now, so the space and ground-based telescopes of the future can be designed to identify the most promising biosignatures,” Schwieterman said.

We have yet to discover concrete evidence of extraterrestrial life out in the cosmos, but by improving the frameworks that we will use with advanced, future telescopes, we are inching ever closer.